This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A364847 #9 Aug 12 2023 01:12:49 %S A364847 1,3,5,8,7,15,9,20,17,21,13,40,15,27,35,44,19,51,21,56,45,39,25,100, %T A364847 37,45,53,72,31,105,33,92,65,57,63,136,39,63,75,140,43,135,45,104,119, %U A364847 75,49,220,65,111,95,120,55,159,91,180,105,93,61,280,63,99,153,188,105,195,69 %N A364847 Number of conjugacy classes in the group SL(2, Z_n), up to conjugacy in GL(2, Z_n). %C A364847 Here two matrices A, B in SL(2, Z_n) are in the same conjugacy class if P^-1*A*P = B for some matrix P in GL(2, Z_n). %F A364847 For an odd prime p : a(p) = p + 2. %o A364847 (Magma) [#[c[3] : c in Classes(GL(2,ResidueClassRing(n))) | Determinant(c[3]) eq 1] : n in [2..50]]; %Y A364847 Cf. A062354, A065501. %K A364847 nonn,mult %O A364847 1,2 %A A364847 _Robin Visser_, Aug 10 2023